Goofy driver side door lock!

[torinoscj429]

Gotta LOVE these electrical gremlins!

I have a 2000 (built 11/99) Merc Mountaineer Monterey. I did some troubleshooting with the balky driver side door lock actuator, and still haven't got 100% function out of it.

Inside the car: push down on D/S LOCK button, 3 doors and liftgate lock, D/S does not lock.

Inside the car: push down on D/S UNLOCK button, 3 doors and liftgate unlock, D/S does not unlock.

Outside car: Keyfob lock, 3 doors and liftgate lock, D/S does not lock.

Outside car: Keyfob unlock, ALL doors and liftgate unlock.

Outside car: Keypad lock (7/8 + 9/0 simultaneously), 3 doors and liftgate lock, D/S does not lock.

Outside car: Keypad unlock (code + 3/4), ALL doors and liftgate unlock.

I took apart the door yesterday, and tried a known good actuator, and got the same results. I disassembled and traced the wires to the big door jamb connector, and found no fault with the door wiring. The wires going into the vehicle would still only UNLOCK the known good actuator.

Knowing that the wires act as positive and negative alternately, getting the thing to UNLOCK should also get it to LOCK...since there are only TWO wires to the actuator, the same wires just switch polarity to change direction.

Since the D/S door will UNLOCK with the keyfob and/or door keypad, this leads me to believe that the wiring is ok.

What should I look for now?

Thanks,

Gerard

 

[swshawaii]

Latch? Look inside the latch and bottom of the door for remnants of a small broken "mystery" spring. If you've ruled out the wiring, actuator, and linkages only the latch remains. Had the same issue where my drivers door wouldn't stay locked. After much trial and error a new latch fixed it. I've read where the GEM module could be the problem but it seems a very uncommon failure. Carefully remove the glass run channel fastened with one bolt for better access and visibility. GL

https://www.explorerforum.com/forums/showthread.php?t=207373

 

[torinoscj429]

When I reversed the polarity of the wires, the lock moved the other direction. There is something in the control system that reverses the polarity of the wires. Anyone know what that is?

 

[bobflood]

Do the PS and/or liftgate lock switches give the same result as the DS lock switch? If not, I would look for a broken wire in the DS door bundle. All of the lock switches, including the DS one, operate lock and unlock relays in the back next to the RAP module. The keypad and the fobs both talk to the RAP module, which in turn controls the lock and unlock relays. There is a separate unlock relay for the DS door lock - that is how the "one push for DS door, two pushes for rest of doors" function via the fob works. Look here for wiring diagrams:
Auto - Online Repair Info
http://search.ebscohost.com/
Login ID: rrcc
Login PW: rebsco
Select: Auto Repair Reference Center
Fill in: Find Your Vehicle
Follow prompts down to Wiring Diagrams.
Good luck!!

 

[torinoscj429]

FIXED!!!

I looked at the relays behind the computer, and there were two each of different sizes. I switched the larger two, and nothing changed.

I switched the smaller of the two, and it all works! I switched them back, and the problem returned. (the two on the right in the attached pic)

So, it's one of the two smaller relays that's bad. Do these have a name?

Thanks,

Gerard

 

[torinoscj429]

FIXED!!!

I looked at the relays behind the computer, and there were two each of different sizes. I switched the larger two, and nothing changed.

I switched the smaller of the two, and it all works! I switched them back, and the problem returned. (the two on the right in the attached pic)

So, it's one of the two smaller relays that's bad. Is it called the Driver's Door Main Relay?

Thanks,

Gerard